1. Field of the Invention
This invention relates to a method for preparing a spherical body, typically golf ball using a split mold. More particularly, it relates to a method for preparing a spherical body wherein a fin that is formed on the spherical body surface along the split mold mating line can be effectively removed.
2. Prior Art
A split mold is often used in the molding of a spherical body such as a golf ball. FIG. 5 schematically illustrates a split mold A consisting of a pair of upper and lower mold halves A1 and A2 which are mated along a parting line C to define a cavity B. After a molding resin is placed in the cavity B, thee mold halves A1 and A2 are tightly closed to mold the resin into a spherical body. At the region of the spherical body thus molded that corresponds to the parting line C of the split mold A, the resin spreads over the parting line C to leave a ring-like fin or burr 2 as shown in FIG. 4. The fin 2 must be removed before the spherical body can be commercially acceptable.
A variety of deburring techniques are known in the art for removing the annular fin from the spherical body. Typical deburring techniques include a grinding technique of abrading off the fin with an abrasive wheel or sand paper while rotating the spherical body; a technique of cutting off the fin by means of a so-called water jet cutter by injection high pressure water (see JP-A 228226/1993); and a technique of removing the fin with a laser beam.
However, the technique using an abrasive wheel or sand paper and a technique using a heat iron have the problem that in deburring the spherical body is machined or melted to an extra region disposed adjacent the fin. In the case of a golf ball, dimples disposed adjacent the fin are adversely affected, detracting from the outer appearance and performance of the golf ball. The technique using a water jet cutter has the alleged advantage that it can remove only the fin without machining adjacent regions. However, since a split mold is inevitably accompanied by a misalignment between the upper and lower mold halves, a step 3 is formed on the spherical surface across the fin 2 as shown in FIG. 4A. In order to remove the step 3, the spherical body must be machined to a relatively large area about the fin 2 to define a relatively wide deburred zone 4 as shown in FIG. 4B. In the case of a gold ball, dimples disposed adjacent the fin can be impaired. A similar problem arises with the laser beam cutting technique, which also suffers from the problem of scorching the surface of a molded piece due to laser heat.
Golf balls and other spherical bodies on which requirements of high quality are imposed need, after removal of a fin, a finishing step of melting the root of the fin to finish the deburred region into a smooth spherical shape. Since the overall process includes two steps, deburring and finishing steps, it is complex and costly to manufacture spherical bodies of quality.